1. Field of the Invention
The present invention relates to rotation sensors and couplings used in rotation sensors, where such rotation sensors may be used as an automotive rotation sensor for steering systems. More particularly, the present invention relates to contact-type automotive rotation sensors and couplings therefor.
2. Discussion of the Background
A general summary of the related art is provided in the two U.S. patent applications cited above, and therefore is not repeated in detail. Furthermore, it is worth noting that conventional couplings used in rotation sensors generally include coupling mechanisms made of metal, where shifting motions in the coupling mechanisms are absorbed by the elasticity of the coupling mechanisms themselves. Thus, the coupling mechanisms are generally complex, 3-dimensional structures made from a single substrate (such as a metal sheet). The complex shapes enable the coupling to prevent relative motion in a rotational sense between a rotor and a base to be restricted, while motion in either one dimension or another dimension of an x-y plane is permitted. This motion in the x-y plane is accomplished by having the coupling absorb the translational movement by compression, and extension of the resilient portions of the coupling. Conventional couplings interconnect an inner member to an outer member by way of “rails” formed in the coupling. A second set of rails interconnects the outer member to a base.
A market for rotation sensors and couplings for use in a rotation sensor is the highly competitive automotive parts industry. The manufacturing environment for products supplied to automotive manufacturers is highly competitive in terms of product price, size and weight, and maintainability. Furthermore, automotive manufacturers often require “second sourcing” for automotive parts to avoid the risk inherent with receiving parts from a sole-source provider. One limitation with being able to obtain quality parts from a “second-source,” is the compatibility of one manufacturer's coupling for use in a general rotation sensor. For example, one coupling may be designed in a compatible fashion with surrounding components, by accounting for weight, moment of the second rotating plate, and friction with the surrounding components, because the shaft and the second rotating plate are interconnected by the elastic coupling component. However, if there is a change in the surrounding parts, the compatibility, and ultimately the reduced reliability of the coupling or the rotation sensor itself, may be compromised.
FIG. 13 shows a portion of an automobile, to which the rotation sensor (and the coupling therefore) may be mounted to a steering handle 10 that is directly coupled to a column shaft 12. The steering shaft is coupled through a torsion bar 14 to the column shaft 12 and on the other end is coupled to an electrically-operated power steering mechanism 18. This power steering mechanism accommodates the rack and pinion for steering front wheels 19 and an electric motor for assisting a steering operation.
During the steering operation, the torsion bar 14 couples the column shaft 12 with the steering shaft 16 and receives a reactive twisting force from a road surface. As a result, a rotational deviation occurs between the column shaft 12 and the steering shaft 16. Rotation sensors serve the general function of identifying the rotational deviation and therefore the reaction torque that is applied to the steering shaft 16 and in turn the steering handle 10.